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Hot13p mediates import and assembly of the small Tim proteins
Author(s) -
KochBeverly Kristen Nicole,
Leverich Edward,
Hwang David,
Curran Sean,
Leuenberger Danielle,
Koehler Carla
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a493-d
Subject(s) - intermembrane space , mitochondrial intermembrane space , translocase of the outer membrane , translocase of the inner membrane , translocase , microbiology and biotechnology , mitochondrial carrier , inner mitochondrial membrane , inner membrane , chemistry , biology , protein targeting , mitochondrion , biochemistry , mitochondrial membrane transport protein , membrane protein , bacterial outer membrane , membrane , chromosomal translocation , escherichia coli , gene
The mitochondrion has two pathways for the import of proteins coded in the nucleus. The general import pathway is utilized by precursors with an amino‐terminal targeting presequence. Precursors are first translocated across the Translocase of the Outer Membrane (TOM) and then through the Translocase of the Inner Membrane (TIM23). The TIM22 import pathway is utilized by inner membrane proteins including the carrier proteins and the import components Tim17p, Tim22p, and Tim23p. Components include a family of small Tim protein in the mitochondrial intermembrane space, Tim8p, Tim9p, Tim10p, Tim12p, and Tim13p, and the inner membrane proteins Tim22p, Tim18p, and Tim54p. The small Tim proteins form soluble complexes in the mitochondrial intermembrane space and function as chaperones to mediate the import and insertion of hydrophobic substrates of the TIM22 import system. The mechanism by which the Tim9p‐Tim10p and Tim8p‐Tim13p complexes assemble and bind to precursors is not well understood, but studies have shown the conserved cysteine residues in the twin CX3C motif are important for their function. Our recent studies have lead to the identification of a new component, Hot13p, of the mitochondrial intermembrane space. The small Tim proteins require Hot13p for assembly into a 70 kDa complex in the intermembrane space. Once assembled the small TIM complexes escort hydrophobic inner membrane proteins en route to the TIM22 complex. These results suggest that the small TIM complexes have a specialized assembly pathway in the intermembrane space. (This work is supported by funds from the NIH GM61721, GM070415, GM070404, and the Arnold and Mabel Beckman Foundation)